Espresso and cappuccino are beverages widely enjoyed in Europe, and are gaining increased acceptance in the United States at this time. Unlike the percolated and drip-brewed coffee most commonly made in America, espresso is made by directing heated water, under pressure, through a layer of compacted ground coffee resting atop a filter disc carried within a filter holder. The ground coffee is placed into the filter holder from a grinder, compacted against the filter disc and then the filter holder is detachably mounted to the espresso machine in preparation for a brewing operation. The residence time of the water within the ground coffee is typically on the order of 20 to 30 seconds to produce brewed coffee or espresso having a taste many Americans find to be "stronger" than percolated or drip-brewed coffee, but which actually has about half the caffeine content.
Cappuccino is usually made by first brewing espresso as described above, and then pouring a layer of foamed milk over the espresso in the cup. In order to make the foamed milk, air is intermixed with the milk in the presence of steam so that the milk is "emulsified," i.e. foamed or frothed, and heated at the same time. The production of foamed milk for cappuccino has evolved over the decades with an emphasis on making the process more automatic and less dependent on the skill of the operator. This is particularly true in the home cappuccino market, and also in markets such as the United States where there are comparatively few skilled operators and limited training of new ones.
The earliest method of making cappuccino involved equipping an espresso machine with a tube connected to a source of steam. In order to make foamed milk with this type of system, the operator places the steam tube into a container of milk, turns on the steam, and then manipulates the container by hand, e.g. in a swirling and/or up-and-down motion, to introduce air into the milk. The steam assists in intermixing the air and milk within the container, and also heats the milk to form a quantity of emulsified or foamed milk which is then poured into a cup containing espresso. This is still the predominant method of making foamed milk in the commercial markets in Europe, but involves a reasonable degree of skill on the part of the operator to avoid splattering of the milk as it is being foamed, burning of the milk and/or the production of foamed milk having less than the desired consistency.
In an effort to simplify the above-mentioned method of making foamed milk, and require less operator skill, apparatus were developed such as disclosed, for example, in U.S. Pat. Nos. 4,735,133 to Paoletti; 4,800,805 to Mahlich, et al.; and 4,945,824 to Borgmann. The foaming apparatus of the type disclosed in these patents includes a steam tube connected at one end to a source of steam and having a discharge outlet at the opposite end, and an air tube having an inlet open to atmosphere and an outlet located near the discharge outlet of the steam tube. The tubes are first inserted within a container of milk, and then the supply of steam is activated so that a flow of steam is introduced through the steam tube. In the course of passage of the steam through the steam tube, a suction is created within the air tube which draws air through such tube and into the container of milk where it is agitated and intermixed with the milk and steam to form heated, foamed milk. In devices of this type, the operator need not manipulate the container of milk to introduce air into the milk because the air is drawn into the milk by the suction developed from the flow of steam. While an improvement over the earlier foaming devices incorporating only a steam tube, it has been found that use of the above-described devices can result in the production of unacceptable foam, e.g. with large bubbles or the like, unless the operator is relatively skilled. Additionally, the milk must be poured into a container and placed under the tube by the operator in order to obtain the foamed milk, and this is labor-intensive and inefficient.
In order to further reduce operator intervention in the making of cappuccino, automatic milk emulsifiers have been developed as disclosed, for example, in U.S. Pat. Nos. 4,715,274 to Paoletti and 4,779,519 to Giuliano. The emulsifier units disclosed in each of these patents eliminate the need for an operator to manipulate or hold a container of milk at all. Such emulsifiers operate by injecting a jet of steam into the interior of the emulsifier housing creating a vacuum which draws a quantity of milk and air therein. The air enters the emulsifier housing through an inlet open to atmosphere, and the milk is drawn from a container through a tube connected to the emulsifier. The air and milk are intermixed and heated within an emulsifying chamber contained within the emulsifier housing. The emulsifying chamber has an outlet through which the foamed milk is transmitted into a container, and then the foamed milk is poured by the operator into a cup containing espresso to make the finished cappuccino. Despite eliminating the need for an operator to in any way manipulate a milk container in order to form the foamed milk, such emulsifier units nevertheless require a separate operation to collect the foamed milk and then pour it into a cup containing espresso to make cappuccino.
This problem has been addressed in U.S. patent application Ser. No. 07/761,366 mentioned above, which is the United States National Phase of PCT Application No. PCT/EP90/00122 entitled "An Automatic Machine for Dispensing Black Coffee, White Coffee, and the Like". In this apparatus, the operator merely places a cup under a discharge spout, touches a control button and separate or combined flows of espresso and foamed milk are deposited directly into the same cup. The foamed milk can be provided by an emulsifier unit such as those disclosed in U.S. Pat. Nos. 4,715,274 and 4,779,519 discussed above, or, alternatively, by any other device capable of making suitable foamed milk. Espresso is obtained from a standard filter unit including a filter holder of the type described above which receives ground coffee from a grinder and is releasably mounted to the apparatus. Preferably, the discharge spout includes separate passageways or tubes for the espresso and foamed milk, located side-by-side, so that both the foamed milk and espresso can be directed into the same cup without operator intervention.
It has been recognized that even with automatic cappuccino machines, the operator must nevertheless manipulate the coffee filter unit by hand, including placing the filter holder into a grinder to receive ground coffee, compacting the ground coffee within the filter holder atop the filter disc, and then placing the filter holder in position on the espresso machine to receive heated water to make espresso. While it take less skill to perform these operations, compared to that of foaming the milk, such hand operations nevertheless increase the time required to make cappuccino and involve at least some level of skill. This can be of particular concern in high volume operations such as restaurants, coffee shops and the like wherein speed of production and consistency of the finished product are particularly important.